Much research work has been performed on liquid crystals at least over the last dozen or so years.
This work has given rise to numerous publications.
Particular mention may be made of the following documents:
(1) APPLIED PHYSICS, vol. 11, No. 1, September 1976, Springer-Verlag, K. Fahrenshon et al: "Deformation of a Pretilted Nematic Liquid Crystal Layer in an Electric Field", pages 67-74; and
(2) JOURNAL OF APPLIED PHYSICS, vol. 47, No. 9 September 1976, American Institute of Physics, S. Matsumoto et al: "Field-induced deformation of hybrid - aligned nematic liquid crystals: New-multicolor liquid crystal display", pages 3842-3845, which deals with an electrically-controlled birefringence effect in nematic liquid crystals taking place, in the volume of a cell containing a liquid crystal material, by coupling between an electric field applied to the cell and the dielectric anisotropy of the liquid crystal.
In addition, some of the results of research work done at the University of Paris Sud Physics of Solids Laboratory are described in French patent application No. 82 07309 filed Apr. 28, 1982 and published under the number 2,526,177, French Pat. application No. 84 16192 filed Oct. 23, 1984, published under the number 2,572,210, and French Pat. application No. 85 09224 filed June 18, 1985, published under the number 2,587,506.
One of the major drawbacks in most electro-optical devices described in the past stems from the fact that their response time to an electric excitation is considerably more than one millisecond. There has been a recent proposal for a system enabling polarized light to be switched rapidly (in the microsecond range) by liquid crystals. This device uses ferroelectricity in a volume of a chiral smectic material with weak surface anchoring, and is described in Ferroelectrics 59 25 (1984) by N. Clark and S. Lagerwall.
However, although this device enables a relatively short response time to be obtained, it suffers from various drawbacks including: difficulty in working with multiplexing; the polar character of the anchoring; the necessity of accurately controlling the anchoring force; and the power consumption of the cells while being maintained by an AC electric field.
Taking account of the limits of prior devices, the inventors seek to provide novel means enabling high frequency electric excitation (up to several MHz) to be used on liquid crystal electro-optical devices.